blocks|key|4511638|text|三个问题:三部分回答：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4511639|从设计的角度来看，这是可以的吗？|4511640|绝对一点儿没错。这没什么问题。如果您需要在枚举上进行大量迭代，流API是一种简洁的方法，并且可以将样板隐藏在一个小方法后面。不过，我会认为OldCumudgeon的version更好。|offset|length|4511641|从性能的角度来看，这是可以的吗？|4511642|这很可能无关紧要。大多数情况下，枚举并没有那么大。因此，在99.9%25的情况下，一种或另一种方法的开销可能并不重要。|4511643|当然，也有0.1%25的人这样做。在这种情况下:用你的真实数据和消费者进行适当的衡量。|4511644|如果我必须打赌，我会认为for+each循环会更快，因为它更直接地映射到内存模型，但在谈论性能时不要猜测，并且在实际需要调优之前不要调优。以一种正确的方式编写代码，首先是正确的，其次是容易阅读的，然后才是代码风格的性能。|style|CODE|4511645|为什么Enums没有正确集成到Stream+API中？|4511646|如果您将Java的Stream+API与许多其他语言中的等价物进行比较，它似乎存在严重的局限性。有各种各样的片段缺失(例如，可重用的流和可选的流)。另一方面，实现Stream+API对API来说无疑是一个巨大的变化。它被多次推迟是有原因的。因此，我猜Oracle希望将更改限制在最重要的用例上。无论如何，枚举并不经常被使用。当然，每个项目都有几个这样的项目，但与列表和其他集合的数量相比，它们算不了什么。即使你有一个Enum，在很多情况下你也不会遍历它。另一方面，列表和集合可能几乎每次都会被迭代。我认为这就是为什么Enums没有获得自己的Stream世界适配器的原因。我们将看到在未来的版本中是否会添加更多这样的功能。在此之前，您始终可以使用Arrays.stream。|4511647|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/823393/oldcurmudgeon|1|https://stackoverflow.com/a/29922602/66686^0|0|0|1X|C|0|2A|7|1|0|0|0|0|C|8|0|0|8Y|D|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|16|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|17|8|@]|9|@$F|18|G|19|1|1A]|$F|1B|G|1C|1|1D]]|A|$]]|$1|H|3|I|5|6|7|1E|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1F|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1G|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1H|8|@$F|1I|G|1J|P|Q]]|9|@]|A|$]]|$1|R|3|S|5|6|7|1K|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|1L|8|@$F|1M|G|1N|P|Q]]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1O|8|@]|9|@]|A|$]]]|W|$X|$5|Y|Z|10|A|$11|12]]|13|$5|Y|Z|10|A|$11|14]]]]

<p>Three questions: three-part answer:</p>

<h3>Is it okay from a design point of view?</h3>

<p>Absolutely. Nothing wrong with it. If you need to do lots of iterating over your enum, the stream API is the clean way to go and hiding the boiler plate behind a little method is fine. Although I’d consider <a href="https://stackoverflow.com/users/823393/oldcurmudgeon">OldCumudgeon</a>’s <a href="https://stackoverflow.com/a/29922602/66686">version</a> even better.</p>

<h3>Is it okay from a performance point of view?</h3>

<p>It most likely doesn’t matter. Most of the time, enums are not that big. Therefore, whatever overhead there is for one method or the other probably doesn’t matter in 99.9% of the cases.</p>

<p>Of course, there are the 0.1% where it does. In that case: measure properly, with your real-world data and consumers.</p>

<p>If I had to bet, I’d expect the <code>for each</code> loop to be faster, since it maps more directly to the memory model, but don’t guess when talking performance, and don’t tune before there is actual need for tuning. Write your code in a way that is correct first, easy to read second and only then worry about performance of code style.</p>

<h3>Why aren’t Enums properly integrated into the Stream API?</h3>

<p>If you compare Java’s Stream API to the equivalent in many other languages, it appears seriously limited. There are various pieces that are missing (reusable Streams and Optionals as Streams, for example). On the other hand, implementing the Stream API was certainly a huge change for the API. It was postponed multiple times for a reason. So I guess Oracle wanted to limit the changes to the most important use cases. Enums aren’t used that much anyway. Sure, every project has a couple of them, but they’re nothing compared to the number of Lists and other Collections. Even when you have an Enum, in many cases you  won’t ever iterate over it. Lists and Sets, on the other hand, are probably iterated over almost every time. I assume that these were the reasons why the Enums didn’t get their own adapter to the Stream world. We’ll see whether more of this gets added in future versions. And until then you always can use <code>Arrays.stream</code>.</p>


blocks|key|4098|text|我会去找EnumSet。因为forEach()也是在Iterable上定义的，所以您可以完全避免创建流：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4099|EnumSet.allOf(Letter.class).forEach(x+->+foo(x));|code-block|syntax|javascript|4100|或者使用方法引用：|4101|EnumSet.allOf(Letter.class).forEach(this::foo);|4102|不过，老式的for-loop感觉更简单一些：|4103|for+(Letter+x+:+Letter.values())+{
++++foo(x);
}|4104|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/util/EnumSet.html^0|4|7|E|9|Q|8|4|7|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]]|E|$]]|$1|F|3|G|5|H|7|1A|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1B|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1D|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1E|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]]]

<p>I'd go for <a href="http://docs.oracle.com/javase/7/docs/api/java/util/EnumSet.html"><code>EnumSet</code></a>. Because <code>forEach()</code> is also defined on <code>Iterable</code>, you can avoid creating the stream altogether:</p>

<pre><code>EnumSet.allOf(Letter.class).forEach(x -&gt; foo(x));
</code></pre>

<p>Or with a method reference:</p>

<pre><code>EnumSet.allOf(Letter.class).forEach(this::foo);
</code></pre>

<p>Still, the oldschool for-loop feels a bit simpler:</p>

<pre><code>for (Letter x : Letter.values()) {
    foo(x);
}
</code></pre>


<p>I'm wondering what the best way is in Java 8 to work with all the values of an enum. Specifically when you need to get all the values and add it to somewhere, for example, supposing that we have the following enum:</p>

<pre><code>public enum Letter {
 A, B, C, D;
}
</code></pre>

<p>I could of course do the following:</p>

<pre><code>for (Letter l : Letter.values()) {
    foo(l);
}
</code></pre>

<p>But, I could also add the following method to the enum definition:</p>

<pre><code>public static Stream&lt;Letter&gt; stream() {
    return Arrays.stream(Letter.values());
}
</code></pre>

<p>And then replace the for from above with:</p>

<pre><code>Letter.stream().forEach(l -&gt; foo(l));
</code></pre>

<p>Is this approach OK or does it have some fault in design or performance? Moreover, why don't enums have a stream() method?</p>


Java 8 way to work with an enum

我想知道在Java8中处理枚举的所有值的最好方法是什么。特别是当您需要获取所有值并将其添加到某个位置时，例如，假设我们有以下枚举：public enum Letter { A, B, C, D;}我当然可以这样做：for (Letter l : Letter.values()) {    foo(l);}但是，我也可以...

问使用枚举的Java 8方法
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